Time measurement system



Sept. 1, 1953 E. F. SHELLEY TIME MEASUREMENT SYSTEM Filed June 4, 1949Time lindicaror 2 Shee'ts-Sheet 1 Motor- Hrmature INVENTOR Eowim F.SHELLEY ATTORNEY P 1, 1953 E. F. SHELLEY TIME MEASUREMENT SYSTEM 2Sheets-Sheet 2 Filed June 4, 1949 R Y L m M N H R W o LF m m. wY DPatented Sept. 1,, 1953 ,tsmz

'rmm MEASUREMENT SYSTEM Edwin F. Shelley, New York, N.

Y., assignor to American Chronoscope Corporation, Mount Vernon, N. Y.,-a corporation of New York- Application June 4, 949, Serial No. 97,200 10Claims. (Cl. 32468) The present invention relates to a simple timemeasurement system capable of measuring time intervals with a relativelyhigh degree of accuracy.

Presently, in design and testing procedures in order to measure timeintervals and particularly time intervals in the millisecond tomicrosecond range, with a degree of accuracy of the order of 1%,cumbersome and time-consuming systems are employed. These make use ofrelatively expensive items of equipment such as stable oscillators,oscilloscopes, counters and other devices. Thus the all-importantvariable of time has not been measurable with the ease and conveniencewith which other standard variables such as voltage, amperage andresistance have been ascertainable.

An object of my invention is to provide a simple, relativelyinexpensive, time measurement system.

A further object of my invention is to provide a time measurement systemcapable of measuring time intervals of the order of seconds tomicroseconds and beyond with a relatively high degree of accuracy.

Another object of my invention is the provision of a time meter whichmay be used with the same ease, convenience and simplicity of employmentas other standard instruments such as voltmeters, ammeters and the like.

Still another object of my invention is the provisionof a time meteradapted to accurately measure short time intervals and display themeasurement mechanically in easily readable form.

Other objects and a fuller understanding of my invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawings which illustrate preferred embodimentsthereof, it being understood that the foregoing statement of the objectsof my invention is intended to generally explain the same withoutlimiting it in any manner.

Fig. 1 is a schematic diagram of a simple time measurement systemembodying my invention.

Fig. 2 is a schematic of a more elaborate embodiment thereof.

Referring to the drawings and more particularly to the embodiment of theinvention shown in Fig. 1, it comprises a balance voltage source I0,having positive and negative terminals respectively II and ii, a balancepotentiometer P across its output, a timing capacitor C switchably inparallel therewith through center arm l4 and contact l5 of single-poledouble-throw 2 charge-discharge switch l3; a timing resistor Rswitchably in parallel with said timing capacitor C through center arm[4 and contact N5 of said switch, a detector circuit including adetector that being the terminalthereof not common to said capacitor andbalance potentiometer P, and

a direct-current detector relay 20 in series between the plate ofdetector tube D and the positive terminal of detector voltage source l1,said relay being adapted to break the contact between its armature 2|and contact 22 when energized. Motor armature 23, which is part of aconventional motor not shown, is connected through said relay contact 22and relay armature 2| to its power, motor voltage source 2t, and itsshaft is mechanically linked, preferably by a system of gears to bothpotentiometer arm is and pointer 25 in time indicator 28, in suchfashion that when said motor armature revolves said arm andpointerrotate an angular distance proportional to the number of suchrevolutions. Time indicator 26 may comprise merely a dial face 21calibrated in suitable time units and said pointer 25 rotatably mountedthereon in conventional fashion. The heater of detector tube D andconnections thereto and power source thereof are not shown, the samebeing conventional.

As is readily apparent, the above-described system is based on thefamiliar principle that the, dimensional product of electricalresistance by electrical capacitance is time. Thus if an initiallycharged capacitor is permitted to discharge through a resistance for anunknown time t, then at the end of said interval the capacitance willhave discharged to a certain fraction of its initial voltage, and thatfraction will be a function only of the capacitance, the resistance andthe discharging time t. It follows that if the values of resistance andcapacitance are known, then discharging time 1. may be ascertained bymeasuring thefraction of the' initial voltage which remains across thecapacitor. The measurement in the present system is done by means of aself-balancingpotentiometer whose center arm is mechanically linked totime indication means.

Thus, if a time interval T is mechanically presented to the system shownin Fig. 1, by maintaining center arm it of charge-discharge switch i3against contact l6 thereof for time T, and if then upon disengagementfrom said contact said arm is left in a position intermediate contactsl5 3 and it, a direct reading of time T may be made from time indicator26.

As shown in Fig. 1, the system is in the ready state, i. e., ready toreceive a time interval to be measured. Since center arm I ofchargedischarge switch I3 is thrown to contact I! the balance voltagesource I is connected across timing capacitor C and said capacitor ischarged to the full voltage of said source. Potentiometer arm it ofbalance potentiometer P is at its upper limit at terminal 29a which isat the same potential as terminal i9 01' timing capacitor C. Sincesaid-terminals are connected to the grid and cathode of detector tube D,those elements are at a voltage parity and the tube is conducting andmaintaining detector relay 20 in an energized state. It follows thatmotor armature 23 is motionless, for when energized, said relay opens alead to motor voltagevsource 24. Time indicator 26 reads zero.

It then while the system is in the ready state, time T is mechanicallypresented to it as above described, the following occurs. When centerarm H of charge-discharge switch moves away from contact l5 thereof itopens the charge circuit of timing capacitor C and leaves C fioating."When said arm meets contact it it closes said capacitors dischargecircuit and so long as it remains closed capacitor C will dischargethrough timing resistor R. However, as timing capacitor C discharges,its terminal l8 becomes less negative in potential with respect topositive terminal ll of balance voltage source ill and, conversely morepositive with respect to said source's negative terminal I! and terminal29a oi. balance potentiometer P, thus raising the potential of thecathode of detector tube D with respect to its grid. Since the grid thennegative with respect to the cathode, detector tube D is either cut oilor the flow of plate current is reduced 'to the point where it isinsuflicient to maintain detector relay in an energized state. In eithercase, the same result obtains, i. e., detector relay 20 opens, thusmaking contact between relay armature 2| and contact 22 and henceenergizing motor armature 23. As said armature rotates, it moves pointer25 off the zero position and drives potentiometer arm I8 of balancepotentiometer P in a direction away from terminal 29a thereof. The gearsystem leading from motor armature 23 to potentiometer arm 18 is sodesigned that it will move the said arm across the voltage gradient ofbalance potentiometer P more slowly than the rate of discharge of timingcapacitor C and hence more slowly than terminal I9 thereof rises inpotential, thus insuring that detector tube D will not conductsufllciently to stop motor armature 23 during the discharge cycle ofsaid capacitor.

When at the end of time interval T center arm ll of charge-dischargeswitch I3 is removed from contact l6 thereof and left in an intermediateposition between the two contacts of said switch, timing capacitor C isagain left floating and since it can be neither charged nor dischargedremains at the fraction of its initial voltage to which it had descendedat the instant of said removal.

Motor armature 23 will continue to drive potentiometer arm l8 until itreaches a point on the timing potentiometer P where the voltage is equalto the voltage at terminal I! of timing capacitor C (both voltages beingtaken with reference to point II, the common terminal of potentiometer Pand timing capacitor C) and then it will stop, for when it reaches sucha point the grid and cathode of detector tube D will be at substantiallythe same voltage and the tube will conduct sufllciently-to energizedetector relay II and thus open the motor armature circuit bringingmotor armature '23 to a halt, and consequently stopping bothpotentiometer arm II and pointer 25. Since dial face 21 is calibrated intime units in accordance with the values of timing resistor R and timingcapacitor C, the duration of time interval T may be read directly fromtime indicator 26.

The system may be reset to the ready state by throwing center arm ll ofcharge-discharge switch I! to contact I! and by reversing the polarityof the motor armature leads which may be done by a conventionalreversing switch (not shown) in said leads and thus drive potentiometerarm [8 and pointer 25 back to their original positions. I

It is obvious that an equivalent system may be set up in which thecircuit elements may be rearranged to charge a timing capacitor Cthrough a resistor R for the duration of the time interval to bemeasured instead of discharging such capacitor for such interval as hasbeen explained above. P would measure the fraction of the voltage 01'the balance voltage source to which said capacitor was charged and thetime indicator may be suitably calibrated in units of time.

The degree of accuracy obtainable with the above-described systems willdepend upon the minimization of a number or error sources. First itshould be observed that balance voltage source it is common to bothbalance potentiometer P and timing capacitor C. This feature makes theimportant measuring operation of the system independent of voltagesource fluctuations or changes. Then, since the accuracy 01' a timereading is directly proportional to the constancy of the product of theresistance of timing resistor R. and the capacitance of timing capacitorC, if the temperature coeflicients of those circuit elements are madeequal and opposite, the product of their values can be heldexceptionally constant under normal working conditions. The errorinvolved will be a constant percentage error for any reading.

Again, the accuracy of a reading is dependent upon the preciseness withwhich the setting oi. potentiometer arm I8 is known. This will depend ingeneral upon the construction of the potentiometer and the calibrationof dial face 21. This error tends to be a percentage of the fullscale ofthe dial i'ace rather than a percentage of the reading taken.

It is also necessary that detector tube D sensitively recognize thecondition oi! zero voltage dili'erence between its grid and cathode.This can be accomplished by employing a tube which pos sesses a highratio of transconductance to plate current in the vicinity of zero gridvoltage, and by using a relay with stable and preferably sharp pull-inand release characteristics. Any residual variation in detectoroperation can be minimized by selecting balance voltage source it sothat it is very large in comparison to the variations in grid voltagerequired to energize or release detector relay 2!).

Obviously, if motor armature 23 continues to rotate appreciably afterits power is cut oil, a major source of error may be introduced. Thismay be minimized in any number of conventional fashions includingdamping and anti-hunt circuits. The combination of shorting the motorarmature and having the armature rotate at a relatively low speed hasbeen found to be ade- In such case the balance potentiometer quate. Ingeneral, leakages across various terminals of circuit components willdetermine the upper and lower limits within which the system ma beemployed.

A more elaborate embodiment of my invention is shown in Fig. 2. Thisform is designed to reand 44a, with a zero reference terminal 32 in-'termediate the cathode of tube 43a and the plate of tube 440, provide avoltage source for timing potentiometer P and charging capacitor C aswell as other circuits to be described. Detector voltage source I I isreplaced by detector power supply 31 which derives its power throughprimary 34 from line source 40 and has positive terminal 35 and negativeterminal 36 and across which are placed voltage-regulator tubes 38 and33 and also bleeder resistors to permit the picking oil of intermediatevoltages. The detector power supply in addition to. providing energy fordetector tube D powers input tube 42.

Motor voltage source 24 is replaced by a motor voltage supply comprisinga diode rectifier tube 43 connected in series with filter capacitor 46across line source 40 and having positive terminal 44 and negativeterminal 45. This tube in addition to powering motor armature 23,supplies its motor field winding 41 and various guard. control and resetcircuits.

Charge-discharge switch l3 of Fig. l which performs three functions,namely, those of receiving the input, placing voltage across timingcapacitor C to charge it and providing the means of placing timingresistor R across said capacitor to present a discharge path therefor,has been replaced by several components to enable the reception andhandling of shorter time intervals. Thus the input circuit in Fig. 2includes a pair of input terminals, 48 and 49, an input switch 55,having sections respectively D, E and F and each such section havingcenter arms, respectively 5|, 52 and 53, and each having contacts,respectively DP, D5, D0, and EP, ES, E and FF, F8, F0, the P contactsbeing the contacts for "pulse" input, the S contacts being those for"short input and the 0 contacts being those for "open input. The inputcircuit also includes input tube 42 which serves to feed the input timeintelligence to a flip-flop circuit comprising fiipflop tube and itsassociated elements which in turn controls charge-switch tube 52 whichreplaces the charge-switch function of charge-discharge switch l3 ofFig. 1. Input tube 42 also feeds the input time intelligence todischargeswitch tube 53 which replaces the dischargeswiteh function ofsaid switch I 3. The heaters of the various tubes and the connectionsthereto and the power source thereof are not shown, the same beingconventional.

The operation of this embodiment may best be understood by tracing thepath of a time input signal therethrough and observing the response ofthe various circuits thereto. As shown in Fig.

6 2, the system is in the ready state. As shown by the shading, section5la of flip-flop tube 51 is conducting, permitting charge-switch tube 52to conduct, the latter having a positive bias on its grid derived frombias diode 54 which is fed from a low voltage output 54a from balancepower supply 30. Hence timing capacitor C is kept charged by the samepower supply through said charge-switch tube. Detector tube D is.conducting sufficiently to keep detector relay 8B energized. Its gridand cathode will be deemed to be at the same potential, although, as isobvious, the grid is biased slightly negatively, in order to establish asuitable operating point for the tube and detector relay 60, preferablyin the order of about one volt, by resistor 55 and large droppingresistor 56 and in addition there is a slight drop in the order oftenths of 9. volt across charge-switch tube 52. Motor armature 23 is notrotating, pointer 25 of time indicator 25 is at zero and center arm I8of timing potentiometer P is at its lowest voltage point, i. e., atterminal 29a thereof. Input tube 42 is conducting, its grid receiving aslight positive bias across resistor 51, a part of the bleeder networkacross the output of detector power supply 31 and through grid resistorSlain series with said grid. Input switch .50 is shown in the pulseposition, indicating that the system is set to receive a voltage pulseandmeasure its duration.

If then such a pulse of time T and 01 suflicient amplitude is introducedacross input terminals 48 and 49, such that terminal 49 is treated asthe positive terminal then the pulse will cut off input tube 42 byraising its cathode higher than its grid overcoming the slight positivegrid bias. The sharper the pulse the more sharply will the tube be cutoil and themore rapidly will the voltage rise at plate terminal 58thereof. The ascending voltage wave front will travel through lead 59,through coupling capacitor 6! and to the plate of flip-flop input tube62. the said voltage wave being differentiated byaction of saidcapacitor 5| and resistor 53 in the plate circuit of said tube. Theincoming pulse drives the plate of the flipflop tube 62 positive, thuscausing this diode to conduct and producing a sharply ascending voltagefront on the grid of tube 64 causing it to strongly conduct and therebysharply driving down its plate and hence driving the grid on section 5Iaof flip-flop tube 5! negative, cutting ofi that section and therebycausing section 5lb to conduct. Since flip-flop tube 5! and itsassociated circuit elements is a conventional flip-flop arrangement, itwill not be more fully described except to state that when theconducting section is cut off, the other section will conduct and willcontinue to conduct until the conducting section is itself cut ofi,thereby sending a positive pulse to the non-conducting section andcausing it to conduct. When section 5lb of said tube conducts, point 85in its plate circuit is driven in a negative direction and remains at arelatively negative voltage potential during such time as the saidsection continues to conduct. From point 65 a negative voltage frontproceeds through lead 56 and resistor 61 to the grid of chargeswitchtube 52 thereby sharply cutting off chargeswitch tube 52 by overcomingthe positive grid bias on the said tube derived from bias diode 54. Saidcharge-switch tube will remain cut oil during such time as section 5lbcontinues to conduct. It will be remembered that the charge path oftiming capacitor 0 runs through said 7 I charge-switch tube, andaccordingly, when the said tube is cut on, timing capacitor C can nolonger charge from balance power supply 33.

The plate terminal is of input tube 42 is directly coupled to the, gridof discharge-switch tube 33 through leads 53 and 83. Hence, at the sametime as a diiferentiated pulse is fed to the ilip-di'op circuit, anundiflerentiated positive pulse, being a replica of the input pulse, istransmitted to the grid of said discharge-switch tube I3 and since theforward edge thereof is a positive front, it will cause the saiddischarge-switch tube to conduct, thereby furnishing a discharge pathfor timing capacitor C through said tube and through the timing resistorR. Dischargeswitch tube 53 will continue to conduct for the duration ofthe positive pulse, 1. e., for theduration of time T, the interval whichis to be measured. When the timing pulse ends, dischargeswitch tube 53will no longer conduct and timing capacitor C will cease discharging.However, as in the previous embodiment, it will retain a per- 'centageof the voltage to which it was initially charged and such voltage willbe a function of time t.

At this point, it should be noted that when the timing pulse terminatesand a negative voltage wave form is presented at the plate of flip-flopinput tube 82, that tube will not transmit the same, it being a diodeand hence section 51b of flip-flop tube II will remain conductingkeeping charge-switch tube 52 in a cut-oil condition so that timingcapacitor C will not be able to again charge until the entire system isreset.

In the meantime, as timing capacitor C started to discharge throughdischarge-switch tube 53 and timing resistor R, terminal IQ of saidcapacitor started to become more positive with respect to terminal 29aof balance potentiometer P. Since said terminals are respectively andeffectively connected to the cathode and grid of detector tube D, thecathode of said tube is raised in potential with respect to its grid,and the said tube is cut oil", or as explained with reference to thefirst embodiment of my invention described, the flow of plate currentthrough said tube is reduced at least to the point where it islnsuilicient to maintain detector relay 60 in an energized state andaccordingly detector relay 30 is de-energized and armature 69 drops downand makes contact with contact 13 thereof breaking its contact withcontact H thereof. This places motor armature 23 across its source ofpower, the motor voltage supply consisting of tube 43 and filtercapacitor 46 across line 30 and the armature begins to runmoving pointer25 of timing indicator 26 off its zero position and moving potentiometerarm i8 of timing potentiometer P away from terminal 29:: thereof and ina direction which enables itto start ascending the voltage gradientacross the said potentiometer. To fully explain the path by which powerto motor armature 23 is applied thereto, it is necessary to introducesome of the guard and reset elements of the system. Zero microswitch I2is a single-pole double-throw switch having an arm 13 and contacts 14and 15. In the ready state of the system, arm 13 is in contact withcontact 15. The microswitch is so placed that its arm does not switchover from contact I to contact 14 until potentiometer arm is of timingpotentiometer P has moved some short distance from its position atterminal 29a thereof. Over-run microswitch 16 is also a single-poledouble-throw switch, having an arm 1.1 and contacts 18 and I9. In theready state of the'system arm 11 is in contact with contact 13. It is solocated that the arm does not switch over to contact 13- until pointer26 of timing indicator 23 has passed its full scale reading. Reset relay33, whose function will be described in greater detail, infra, is arelay having four sections respectively, G, H, I and J, whose armaturesrespectively ll, 32, 33 and 34 are mechanically linked and make contactwhen in a de-energized state (as shown in Fig. 2) with contactsrespectively II, 33, 31 and 33, and when energized with contactsrespectively 33, 33, II and 32.

Contact I. of detector relay II is connected through lead 34, througharm 11 and contact 13 of over-run microswitch 13, through lead 33 andthrough contact I! and arm 13 of zero microswitch H to positive terminal44 of motor voltage supply filter capacitor 43. When armature 33 makescontact with contact 13 of said detector relay, since said armature isconnected through lead 33 and section J or reset relay 33 to oneterminal of motor armature 23, power is therefore connected to saidterminal when detector relay 60 is de-energized. The other terminal ofsaid motor armature is connected to the negative terminal 45 of motorvoltage supply filter capacitor 48 by a path which follows lead 95athrough sec? tion I of reset relay 3. through contact 13 of over-runmicroswitch l8 and through surge lamp 36, preferably an incandescentlamp having a tungsten filament, and then through leads 31 and 98. Atthe same time a parallel power path for the motor armature to positiveterminal 43 of motor voltage supply filter capacitor 33 is providedthrough armature 99 and contact III! of holding relay II, the said relaybeing energized when armature 63 of detector relay 60 makes contact withcontact I. thereof. The said alternate positive power path for saidmotor armature runs from said terminal 44 along leads I32 and I M toarmature 33 of holding relay Ill and then through its contact Hill tocontact 13 of overrun miseroswitch 13 at which point it joins thefirstmentioned path which originates through zero microswitch l2 andcontact 13 thereof. This parallel path is necessary, for shortly aftermotor armature 23 commences to revolve and move pointer 25 from its zeroposition. arm 13 of zero microswitch l2 breaks contact with contact IIand makes contact with contact H and if there were no alternate path,the first-described power path to said armature would be open.

As in the first embodiment described, motor armature 23 continues todrive potentiometer arm I! until it reaches a point on timingpotentiometer P where the voltage is equal to the voltage at terminal llof timing capacitor C, said voltages being taken with reference to pointIII, the common terminal of timing potentiometer P and timing capacitorC. Whenthis point on timing potentiometer P is reached, the grid andcathode of detector tube D are at the same voltage and the said tubeagain conducts sumciently to energize detector relay 6|, removingarmature 33 thereof from contact II, thus opening the power circuit tomotor armature 23 and de-energizing holding relay i 0| as well asshorting said motor armature by making contact with contact 1|, thusabruptly bringing said motor armature to a halt and simultaneouslyhalting the further movement of both potentiometer arm l3 and pointer25. At this point a reading of the time interval T which was originallyintroduced to the system by means of the voltage pulse to be measuredmay now be made directly from the graduation on dial face 21 beneathpointer 23.

9 By designing the motor armature 28 .to move pointer 25 so slowly thatit might take some three seconds to traverse the full scale of timeindicator 26, then even if said armature coasted for three millisecondsafter it has been disconnected from its source of power and has beenshorted, there would be an error of only of 1% of full-scale reading.The treatment of minimization of error sources set forth above inconnection with the description of the embodiment shown in Fig. 1obtains in connection with the embodiment of Fig.2.

The guard circuit is included to insure that the reading on timeindicator 26 will remain until the system is reset. If a second timepulse should be presented to the system before it i reset, or if theinstrument should be left without resetting for a sumcient time topermit timing capacitor C to leak sufllciently to cut ofl detector tubeD and hence energize detector relay 60, motor armature 23 would not runfor the reason thatthe arm of zero microswitch 12 is now at contact 14and there would be no positive power path to the motor armature, itbeing remembered that holding relay IN would now again be open.

Additional accuracy may be obtained if only the first third of thedischarge curve of timing capacitor C is employed, since said firstthird is substantially linear. This is insured by calibrating timeindicator 26 so that only one-third of the discharge curve of timingcapacitor C is traversed when pointer 25 reads full scale and by placingover-run microswitch 16 to be actuated to remove arm 11 thereof fromcontact 19 and place it on contact 18 when the said pointer just passesfull scale. When over-run microswitch I6 is so actuated, it opens thepower path of said motor armature and shorts the said armature.

After a reading has been taken, before presenting another timing pulse,it is necessary to reset the system. This is done by pressing resetbutton I03 which has the effect of actuating reset relay 80, it beingremembered that at this time arm 73 of zero microswitch I2 is restingagainst contact 16 thereof. This brings all of the four armatures of thesaid relay into contact with the upper contacts shown adjacent to themin Fig. 2. Section G of said relay operates as a holding relay so thatwhen reset button I03 is released, the said relay remains energized.Secidnn H of said relay acts to short leads I M and I and hence shortsresistor I06 in the grid circuit of section Bib of flip-flop tube 5!,the eflect of which is to produce a drop in grid potential and hence areversal of the flip-flop circuit so that section Bib is cut ofi andsection 5la then conducts. Sections 1 and J serve to reverse thepolarity .of the leads to motor armature 23 and hence start the samerotating in a direction opposite to its previous direction of rotation,thus driving potentiometer arm I8 of timing potentiometer P and pointer25 of time indicator 26 towardtheir zero positions. This reverserotation will continue until zero microswitch I2 is engaged, themicroswitch being set to be engaged at approximately the zero positionof potentiometer arm l8 and pointer 25. When said microswitch is soengaged, arm 73 thereof is switched from contact 18 to contact 15, thusdeenergizing reset relay 80 and cutting off power to motor armature 23.The system would then again be in the ready state.

The operation of the system has been described with input switch 50 inthe pulse position. If input switch 50 is placed in the "short position,

aeanoaa i. e., so that in each of it sections the center arms engagerespectively contacts DS, ES and FS. then the system will measure theduration of a short circuit across input terminals 48 and 49. This is sofor the reason that when switch '50 is thrown to the said short positionand input terminal 48 shorted to input terminal 49, the grid of inputtube 62 is connected through the D section of said switch through theinput terminals and the E section of said switch to point I 01 whichisat the potential of the negative terminal of detector power supply 31,while the cathode of said tube through section F of said switch isconnected to point I08 on the bleeder' across said power supply thuseffectively biasing the said cathode positively with respect to saidgrid by the voltage developed across resistor I06, and hence cutting oiltube 42 and starting the timing cycle of the system as above described.When the short circuit is removed, input tube 42 will again conduct andas above described, the system will indicate the duration of the shortcircuit.

When switch 50 is placed in the open" position, namely where the centerarms of the D, E and F section-s rest against contacts DO, E0 and F0respectively, the system will measure the duration of an open circuitbetween the input terminals. This is so for when the input terminals areopened, with the said input switch in said position, the cathode circuitof input tube &2 is open and the tube ceases conduction, thereby settingin motion the timing cycle above described. When contact between inputterminals 48 and G9 is restored, the tube will again conduct and hencein the manner above described, the system will indicate the duration ofthe open circuit.

I have shown preferred embodiments of my invention, but it is obviousthat numerous changes, omissions, alterations and refinements may bemade without departing from its spirit. Thus various of the criticalresistances of the circuit might have variable resistors in series withthem so that they might be adjusted from time to time. Again it isobvious that by providing a plurality of timing resistors of differentvalues instead of the single timing resistor R, as shown, and byproviding a plurality of timing capacitors of different values insteadof timing capacitor C and arranging said components through a suitabletwo-pole range switch, the system may be given a variety of rangesselectable by variously positioning the switch.

When in the claims reference is made to the fact that one circuitelement is connected to another, or through another or to a terminal ofanother, it is not meant to indicate that there are no circuit elementsbetween such elements so indicated to be connected and there may beother circuit elements between said elements.

Although I have described my invention with a certain degree ofparticularity, it is understood that the present disclosure has beenmade only by way of example and that numerous additional changes in thedetails of design, construction, combination and arr gement of parts maybe resorted to without anscending the scope of the invention ashereinafter claimed.

I claim as my invention:

1. A time measurement system comprising reception means to receive asignal delineating a time interval, including means to transmit saidsignal in the form of a voltage pulse equal in width to the duration ofsaid time interval, a'

timing capacitor, a first voltage source to charge said capacitor, atiming resistor, means responsaid second switch means being adapted toclose upon receiving the forward edge of apulse from said receptionmeans and to open and remove said resistor from said capacitor at thetermination of saidpulse and means to measure the voltage across saidcapacitor atthe end of said period of time including a potentiometerhaving a resistance element and a movable arm in contact therewith, saidfirst voltage source being connected across said resistance element, andmeans associated with said capacitor and potentiometer adapted to movethe arm of said potentiometer across said resistance element to avoltage point thereon which bears a predetermined relationship to thevoltage across said capacitor at the end of said period of time.

2. A time measurement system as described in claim 1, said meansassociated with said capacitor to move said potentiometer arm beingrelated to said arm so as to move the same across the potential gradientof said resistance element more slowly than the change of voltage acrosssaid capacitor.

3. A time measurement system comprising reception means to receive asignal delineating a time interval, including means to transmit saidsignal in the form of a voltage pulse equal in width to the duration ofsaid time interval, a timing capacitor, a first voltage source to chargesaid capacitor, a timing resistor, means responsive to said signal tocause the discharge of said timing capacitor through said resistor for aperiod of time equal to said time interval comprising first switch meansintermediate said timing capacitor and said first voltage source, aflip-flop circuit controlling said switch means and adapted to open thesame upon receiving the forward edge of a pulse from said receptionmeans and hence remove said first voltage source from said timincapacitor, second switch means connecting said timing resistor acrosssaid capacitor when said second switch means are closed, said secondswitch means being adapted to close upon receiving the forward edge of apulse from said reception means and to open and remove said resistorfrom said capacitor at the termination of said pulse and means tomeasure the voltage across said capacitor at the end of said period oftime including a potentiometer having a resistance element and a movablearm in contact therewith, said first voltage source being connectedacross said resistance element, said timing capacitor having a firstterminal common to one terminal of said resistance element and a secondterminal not common thereto, a motor coupled to said arm and adapted tomove said arm along said resistance element and detector meanscomprising a detector tube having at least a control grid, a cathode andan anode, the gridcathode circuit thereof including in series said arm,the portion of said resistance element between said arm and saidfirstterminal and said timing capacitor, and the cathode-anode circuitthereof including a detector voltage source and a relay adapted to closewhen the cathode-anode current reaches a first predetermined level and,

to thereby energize said motor, and adapted to open when said currentreaches a second predetermined level, said detector tube being biased soas to conduct to the extent necessary to close said relay when a firstpredetermined voltage is presented across its grid and cathode and henceenergize said motor and move said arm and to open said relay when asecond predetermined voltage is presented across its grid and cathodeand hence de-energize said .motor and halt the movement of said armjsaidlevel of cathodeanode current and said bias point being so selected thatthe point on said resistance element at which said arm is halted willbear a predetermined relationship to said voltage across said capacitorat the end of said period of time.

4. A time measurement system as described in claim 3, said motor beingcoupled to said arm so as to move the same across the potential gradientof said resistance element more slowly than the change in timing voltageacross said timing capacitor.

5. A time measurement system comprising reception means to receive asignal delineating a time interval, including means to transmit saidsignal in the form of a voltage pulse equal in width to the duration ofsaid time interval, a timing capacitor, 9. first voltage source tocharge said capacitor, a timing resistor in the charge path of saidcapacitor, means responsive to said signal to cause the timing capacitorto charge from said first voltage source through said timing resistorfor a period of time equal to said time interval comprising switch meansintermediate said timing capacitor and said first voltage source, acontrol circuit adapted to close said switch means and connect saidcapacitor to said voltage source through said timing resistor uponreceiving the forward edge of a pulse from said reception means andadapted to open said switch means and disconnect said capacitor fromsaid first voltage source at the termination of said pulse and means tomeasure the voltage across said capacitor at the end of said period oftime including a potentiometer having a resistance element and a movablearm in contact therewith, said first voltage source being connectedacross said resistance element, and means associated with said capacitorand potentiometer adapted to move the arm of said potentiometer acrosssaid resistance element to a voltage point thereon which bears apredetermined relationship to the voltage across said capacitor at theend of said period of time.

6. A time measurement system as described in claim 5, said meansassociated with said capacitor to move said potentiometer arm beingrelated to said arm so as to move the same across the potential gradientof said resistance element more slowly than the change of voltage acrosssaid capacitor.

' 7. A time measurement system comprising reception means to receive asignal delineating atime interval, including means to transmit saidsignal in the form of a voltage pulse equal in width to the duration ofsaid time interval, a timing capacitor, a first voltage source to chargesaid capacitor, a timing resistor in the charge path of said capacitor,means responsive to said signal to cause the timing capacitor to chargefrom said first voltage source through said timing resistor for a periodof time equal to said time interval comprising switch means intermediatesaid timing capacitor and said first voltage source, a control circuitadapted to close said switch means and connect said capacitor to saidvoltage source through said timing resistor upon receiving the forwardedge of a pulse from said reception means and adapted to open saidswitch means and disconnect said capacitor from said first voltagesource at the termination of said pulse and means to measure the voltageacross said capacitor at the end of said period of time including apotentiometer having a resistance element and a movable arm in contacttherewith, said first voltage source being connected across saidresistance element, said timing capacitor having a first terminal commonto one terminal of said resistance element and a second terminal notcommon thereto, a motor coupled to said arm and adapted to move said armalong said resistance element and detector means comprising a detectortube having at least a control grid, a cathode and an anode, thegrid-cathode circuit thereof including in series said arm, the portionof said resistance element between said arm and said first terminal andsaid timing capacitor, and the cathode-anode circuit thereof including adetector voltage source and a relay adapted to close when thecathode-anode current reaches a first predetermined level and to therebyenergize said motor, and adapted to open when said current reaches asecond predetermined level, said detector tube being biased so as toconduct to the extent necessary to close said relay when a firstpredetermined voltage is presented cross its grid and cathode and henceenergize said motor and move said arm and to open said relay when asecond predetermined voltage is presented across its grid and cathodeand hence deenergize said motor and halt the movement of said arm, saidlevel of cathode-anode current and said bias point being so selectedthat the point on said resistance element at which said arm is haltedwill bear a predetermined relationship to said voltage across saidcapacitor at the end of said period of time.

8. A time measurement system as described in claim 7 said motor beingcoupled to said arm so as to move the same across the potential gradientof said resistance element more slowly than the change in timing voltageacross said timing capacitor.

9. A time measurement system comprising receiving means to receive asignal delineating a time interval and having an output which is afunction of said interval, a timing capacitor, means responsive to saidsignal to change the voltage across said capacitor, including switchmeans, a first source of voltage connected to charge said capacitor, atiming resistor connected to one terminal of said capacitor andconnected to the other terminal thereof through said switch means, saidswitch means being connected to said receiving means so as to receivethe output signal thereof, said switch means being actuated by saidoutput to place said resistor in closed circuit with said capacitor fora period of time which is a function of said time interval, thus causinga change in the voltage across said capacitor as a function of said timeinterval, and

means to measure said changed voltage including a potentiometer having aresistance element and a movable arm in contact therewith, a source ofvoltage con ss said resistance elemeans connected across the seriescircuit including the portion of said resistance element between the armthereof and said element terminal and said capacitor and deriving fromsaid series circuit its input consisting of the algebraic sum of thevoltage drops across the component parts thereof, a motor controllableby said detector means coupled to said arm and adapted to move said armalong the resistance element of said potentiometer, said detector beingadapted to activate said motor and hence move said arm when a firstpredetermined voltage appears across the input of said detector and todeactivate said motor and hence halt the movement of said arm, when asecond predetermined voltage appears across said input, at a voltagepoint on said resistance element which bears a predeterminedrelationship to said changed voltage across said capacitor.

10. A time measurement system comprising receiving means to receive asignal delineating a time interval and having an output which is afunction of said interval, a timing capacitor, means responsive to saidsignal to change the voltage across said capacitor. including switchmeans, a first source of voltage connected to charge said capacitor, atiming resistor connected to one terminal of said capacitor andconnected to the other terminal thereof through said switch means, saidswitch means being connected to said receiving means so as to receivethe output signal thereof, said switch means being actuated by saidoutput to place said resistor in closed circuit with said capacitor fora period of time which is a function of said time interval, thus causinga change in the voltage across said capacitor as a function of said timeinterval, and means to measure said changed voltage including apotentiometer having a resistance element and a movable arm' in contacttherewith, a source of voltage connected across saidresistance element,said timing capacitor having a first terminal connected to saidresistance element and having a second terminal not connected thereto,detector means connected across said arm and said second terminal ofsaid timing capacitor, a motor controllable by said detector meanscoupled to said arm and adapted to move said arm along the resistanceelement of said potentiometer, said detector being adapted to activatesaid motor and hence move said arm when a first predetermined voltageappears across the input of said detector and to deactivate said motorand hence halt the movement of said arm, when a second predeterminedvoltage appears across said input, at a voltage point on said resistanceelement which bears a predetermined relationship to said changed voltageacross said capacitor.

- EDWIN F. SHELLEY.

References Cited in the file of this patent UNITED STATES PATENTS

